An “electronic nose” is known as a device formed by one or more sensor and a pattern recognition routine. An “electronic tongue” is a device similar to the electronic nose, but capable of operating in a liquid medium, and enables the analysis of solutes in a solution.
Various types of such devices have been developed and are described for example in the following publications:
U.S. Pat. No. 6,167,747 discloses a vapor recovery system that utilizes a crystal oscillator for sensing the presence of hydrocarbon in the vapor emissions emanating from a fuel tank during refueling. The crystal oscillator is coated with a layer of material having sensitivity for hydrocarbon. In response to any interaction between the coating layer and hydrocarbon, the crystal oscillator experiences a shift in its oscillation frequency relative to the fundamental resonance frequency. The frequency shift is representative of the hydrocarbon concentration in the vapor emissions. A control signal based on the frequency shift is generated and then used to adjust the operating speed of the vapor pump.
U.S. Patent Publication No. 2004/0069046A1 discloses a portable vapor sensing device conveniently adapted for use in sensing the presence and concentration of a wide variety of specified vapors. The device provides these benefits using a sensor module that incorporates a sample chamber and a plurality of sensors located on a chip releasably carried within or adjacent to the sample chamber. Optionally, the sensor module can be configured to be releasably plugged into a receptacle formed in the device. Vapors are directed to pass through the sample chamber, whereupon the sensors provide a distinct combination of electrical signals in response to each. The sensors of the sensor module can take the form of chemically sensitive resistors having resistances that vary according to the identity and concentration of an adjacent vapor. These chemically sensitive resistors can each be connected in series with a reference resistor, between a reference voltage and ground, such that an analog signal is established for each chemically sensitive resistor. The resulting analog signals are supplied to an analog-to-digital converter, to produce corresponding digital signals. These digital signals are appropriately analyzed for vapor identification.
WO 04/057319 discloses a piezoelectric sensor arrangement for analysis of fluid samples. The sensor arrangement includes a signal source, a measuring device and a docking system, which comprises a first part provided with means for receiving a sensor element that exposes a piezoelectric quartz crystal and a second part comprising fluid channels for the sample and a flow cell element, which preferably is removable and which comprises a recess, and inlet and outlet fluid channels for leading a fluid through the recess. The first and second parts are movable in relation to each other between a closed position and an open position and are arranged such that in the closed position the recess of the flow cell element is sealingly covered by the piezoelectric quartz crystal so that a flow cell is formed by said flow cell element and said quartz crystal.
U.S. Pat. No. 6,073,499 discloses a portal for use with a detector for detecting trace amounts of contraband that may be retained on skin or clothing of the human subject. The portal relies upon the continuous process by which microscopic flakes of skin continuously separate from human subjects. The portal further relies upon the existence of a human thermal plume consisting of a layer of warm air adjacent the all human subject. The warm air rises in the cooler surrounding air and transports the microscopic flakes of skin upwardly. The portal capitalizes on this phenomenon by providing at least a partial enclosure with a funnel-shaped collector above the human subject. A low speed flow of relatively dense cool air may be introduced into the portal to buoyantly lift the warmer air of the human thermal plume upwardly. The air stream defined by the human thermal plume and the skin particles therein moves to a trap in the funnel-shaped collector above the portal. The trap cooperates with a detector for detecting the presence of molecules of interest.
U.S. Pat. No. 6,831,273 discloses an apparatus for detecting whether substances of interest are present in a sample of air. The apparatus includes a detector, such as an ion trap mobility spectrometer. The detector is operated at a high drift voltage and then is switched to a low drift voltage. Spectra are collected at the high and low field strengths and are compared with standard spectra at those strengths to determine whether materials of interest are present.
U.S. Pat. Nos. 6,708,572 and 6,840,122 disclose portal trace detection systems for detection of imbedded minute particles of interest, such as traces of narcotics, explosives and other contraband. The apparatus includes a portal through which a human suspect will pass. A detection apparatus is disposed at least partly in the ceiling of the portal, and hence above the human subject in the portal. Particles of interest will be entrained in the human thermal plume that exists in the boundary layer of air adjacent the suspect, and will flow upwardly from the suspect to the detection apparatus in the ceiling of the portal. The portal includes a plurality of vertically aligned arrays of air jets. The air jets are fired sequentially from bottom to top to produce short bursts of air sufficient to disturb the clothing of the suspect and to dislodge particles of interest from the clothing. The dislodged particles of interest are entrained in the air in the human thermal plume and are transported upwardly to the detector.
U.S. Pat. No. 6,526,828, assigned to the assignee of the present application, discloses sensitive and selective method and device for the detection of trace amounts of a substance. The device includes a piezoelectric crystal element comprising at least one crystal resonator in the form of an inverted mesa structure, which has a membrane-like region and is characterized by a certain resonance frequency value. A surface region of the crystal resonator is modified by reactive molecules of a kind capable of interacting with the foreign material to yield a reaction product that effects a change in the resonance frequency of the crystal resonator from said certain resonance frequency value. This change is indicative of the identity and quantity of the foreign material.